OPTIMIZATION OF SEISMIC ACQUISITION METHODS WITH EMPHASIS ON SHALLOW APPLICATION

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DEM - Demonstration contracts

Objective

The objective of the R&D programme is to optimize seismic reflection acquisition methods for accurate delineation of shallow deposits in a macromodel and, by using this information, to improve the quality of deep seismic reflection data.Use will be made of elastic data analyse and data processing techniques for the determination of the macromodel of the shallow subsurface.Much attention will be paid to facilities for quality control (acquisition procedure and data).For the determination of a detailed macro model of the data to be acquired with the system, a travel time inversion scheme for P and S waves is operational. The macro model of the shallow subsurface using both P and S waves is accompanied with validity assessments. The work has been reported in detail.A cost effective system that allows acquiring seismic data on land:- of high quality- with high productivity- using modern data acquisition proceduresthat is available and proved itself during a fieldtest.The main characteristics of the system are :- the system is light weight and consists of only a very limited number of field items- it has a user-friendly user interface- it has a flexible way of active spread selection- it was tested in the field and proved 'field-reliable'- it is a 24 bit system, obtained using a minimal amount of analogue electronics applying a novel A/D concept.- data quality assurance routines were developed and tested on real data and prove to be very useful.Deep seismic reflection surveys for hydrocarbons exploitation and reservoir delineation are severely hampered in areas with a complex shallow subsurface, due to strong lateral (and vertical) varying properties. For the removal of the effects caused by these variations detailed information about the structure and the seismic parameters of the shallow deposits is needed (detailed macromodel). This information can be obtained by optimizing high resolution seismic reflections methods, for the determination of this detailed macromodel. In numerous cases this accurate knowledge about shallow deposits is indispensable for the interpretation and inversion of deep seismic data.The important improvements that have to be realized for the efficient determination of an accurate macromodel of the shallow subsurface are:- development of a data acquisition system for efficient recording of two component high resolution seismic data of high quality utilizing the proposed data acquisition procedure;- developments of techniques for the determination of a detailed macromodel of the shallow subsurface by using inversion of techniques on two component shot data.The acquisition system main developments include data quality control facilities implemented on an open central unit. Concerning the remote units, attention is paid to the development of light weight low power cost effective units.For the determination of macromodels from the acquired data the following processing steps must be adapted for pre-stack shot ordered data:- decomposition of two component dataset in P and S waves;- adaptive tracking of events resulting in P and S wave travel time packs;- estimation of coupled P/S macromodel;- macromodel verification.The development techniques and instrumentation will be tested.